"The accusations against David Wu are both jarring and exceptionally serious," the joint statement says.

"While he, like every American, deserves an opportunity to address those accusations and defend himself, our constituents in the first district of Oregon deserve a member in the House of Representatives whose main focus is fighting for their interests.

"This is a critical time for our state and our nation and Oregonians need every member of their Congressional delegation to be effective. While no one takes pleasure in asking a colleague to resign, we believe he can no longer be an effective representative for our shared constituents and should, in the best interest of Oregon, step down."